1. Field of the Invention
The present invention relates to a method and apparatus for allowing non-contact non-destructive inspection of the deposition state of a conductive thin film formed, for example, on a semiconductor substrate or a glass substrate.
2. Description of the Related Art
These days, in the technical field of semiconductors, electron or optical devices have employed silicon wafers having conductive thin films formed thereon, for example, by sputtering, CVD, or plating.
For such devices, it is important to produce as many devices of the same quality as possible. To this end, it is required to thoroughly control the thickness and electrical properties of the thin films formed on the substrate.
Conventionally known is a method comprising the following steps. First, a number of substrates coated with a conductive film are prepared in one batch at the same time. Then, the film of one of the substrates is destroyed to inspect and analyze the thickness and the electrical properties thereof using a technique such as the four probe measurement or a stylus profiler. Thus, the results of the analysis are adopted as a typical value to estimate the quality of the substrates.
However, this method presents a problem in that some defective substrates cannot be found even when those substrates do not satisfy the predetermined quality.
On the other hand, also known are methods for allowing the non-contact measurement of the thickness of films formed on the substrate. For example, the methods include the X-ray interference method or the laser excitation method.
However, these methods provide very slow measurement speeds at too high a cost; and thereby, cannot be used for mass production.
The present invention was developed to solve such conventional technical problems as described above. It is therefore an object of the present invention to provide a technique which is capable of measuring the thickness of conductive thin films, formed on a substrate, efficiently at low costs.
In order to attain the object, in a first aspect,the present invention provides a film thickness measuring apparatus comprising an eddy current coil sensor, disposing at a predetermined position near a film to be measured, for generating a predetermined eddy current in the film and for detecting a magnetic field caused by the eddy current, and a displacement sensor for measuring a displacement between the eddy current coil sensor and the film to be measured, wherein a thickness of the film is measured in accordance with a variation in inductance of the eddy current coil sensor and the amount of displacement measured by the displacement sensor.
The film thickness measuring apparatus according to a second aspect of the invention, wherein the thickness of the film is measured with a constant relative distance being maintained between the film and the eddy current coil sensor.
The film thickness measuring apparatus according to a third aspect of the invention, wherein a portion of the film to be measured where the eddy current coil sensor generates an eddy current and a portion of the film to be measured where the displacement sensor measures a displacement coincide with each other.
The film thickness measuring apparatus according to a fourth aspect of the invention, wherein the displacement sensor is a laser displacement sensor for emitting a laser beam to the film to be measured to thereby measure a displacement.
The film thickness measuring apparatus according to a fifth aspect of the invention, wherein the displacement sensor is an electrostatic capacitance displacement sensor for detecting an electrostatic capacitance between the displacement sensor and the film to be measured to thereby measure a displacement.
The film thickness measuring apparatus according to a sixth aspect of the invention, wherein the laser beam emitted from the laser displacement sensor penetrates the eddy current coil sensor.
The film thickness measuring apparatus according to a seventh aspect of the invention, wherein the eddy current coil sensor and the electrostatic capacitance displacement sensor are disposed in a coaxial relation to each other.
The present invention provides, in an eighth aspect, a film thickness measuring apparatus comprising an eddy current coil sensor, disposing at a predetermined position near a film to be measured, for generating a predetermined eddy current in the film and for detecting a magnetic field caused by the eddy current; a displacement sensor for measuring a displacement between the eddy current coil sensor and the film to be measured; and a movement mechanism for adjusting an amount of a relative displacement between the eddy current coil sensor and the film. A thickness of the film is measured in accordance with a variation in inductance of the eddy current coil sensor and the amount of displacement measured by the displacement sensor.
The film thickness measuring apparatus according to a ninth aspect of the invention, wherein the thickness of the film is measured with a constant relative distance being maintained between the film and the eddy current coil sensor.
The film thickness measuring apparatus according to a tenth aspect of the invention, wherein a portion of the film to be measured where the eddy current coil sensor generates an eddy current and a portion of the film to be measured where the displacement sensor measures a displacement coincide with each other.
The film thickness measuring apparatus according to an eleventh aspect of the invention, wherein the displacement sensor is a laser displacement sensor for emitting a laser beam to the film to be measured to thereby measure a displacement.
The film thickness measuring apparatus according to a twelfth aspect of the invention, wherein the displacement sensor is an electrostatic capacitance displacement sensor for detecting an electrostatic capacitance between the displacement sensor and the film to be measured to thereby measure a displacement.
In the film thickness measuring apparatus according to a thirteenth aspect of the invention, the laser beam emitted from the laser displacement sensor penetrates the eddy current coil sensor.
In the film thickness measuring apparatus according to fourteenth aspect of the invention, the eddy current coil sensor and the electrostatic capacitance displacement sensor are disposed in a coaxial relation to each other.
This invention is adapted to measure the thickness of a film to be measured in accordance with a variation in inductance of the eddy current coil sensor and the amount of displacement measured by the displacement sensor. This makes it possible to measure the thickness of a film more quickly than by the prior-art non-contact film thickness measuring apparatus.
The present invention makes it also possible to measure the film thickness at low cost in a simple configuration.
According to this invention, the relative distance between the eddy current coil sensor and the film to be measured can be maintained at a constant value. This makes it possible to measure a variation in inductance of the eddy current coil sensor always under the same condition. Consequently, it is possible to measure the thickness of a film with better accuracy.
As this invention, it is possible to measure the thickness of a film always under the same condition. Consequently, quick film thickness measurement with better accuracy can be accomplished when measuring a thickness of a film using the film thickness measuring apparatus according this invention; and the thickness of the film is measured with a constant relative distance being maintained between the film to be measured and the eddy current coil sensor.
According to this invention, after measuring the displacement, the thickness of the film to be measured can be measured at a predetermined portion without moving the film thickness measuring apparatus relative to the film to be measured. This makes it possible to measure the film thickness more quickly.
According to this invention, since the laser displacement sensor is employed, distances can be measured with high spatial resolution and high accuracy.
According to this invention, it is possible to easily coincide the portion of the film to be measured where the eddy current coil sensor generates an eddy current with the portion of the film to be measured where the laser displacement sensor measures a displacement.
According to this invention, since the electrostatic capacitance sensor is employed, it is possible to arrange the eddy current sensor and the electrostatic capacitance sensor in a coaxial relation to each other and provide a compact easily-attachable film-thickness measuring apparatus.
According to this invention, it is possible to easily coincide the portion of the film to be measured where the eddy current coil sensor generates an eddy current with the portion of the film to be measured where the electrostatic capacitance displacement sensor measures a displacement.